Jet Grouting at the West Toronto Diamond Grade Separation Project

"The West Toronto Diamond project, under construction since 2006 and due to be complete in 2015, is a rail-to-rail grade separation project in the heart of urban Toronto. Once complete, a depressed corridor over 1000 metres long will take the CN tracks beneath the CPR tracks. An interlocking steel pile wall serves to retain ground and cut off groundwater. Remedial measures, constructed using jet grouting, were required at several locations within and behind the steel piles.At mechanical interlock joints damaged or suspected of being damaged, jet grouting was used to improve native soils on the retained side of the wall to reduce permeability of the soil mass in intimate contact with the joints to 10-7 cm/s. At a number of steel piles where groundwater and soil type combined to cause basal instability inside the pipes during the interim between excavation and concreting, jet grouting was used to construct temporary bottom seals. At locations near adjacent structures where the steel pile installation process resulted in disturbed ground on the retained side of the wall, jet grouting was used to strengthen and stabilize ground.This paper outlines the details of the various jet grouting applications, the respective testing programs implemented to demonstrate in situ permeability and strength of the soil-grout matrix, and performance of the constructed system.INTRODUCTIONThe West Toronto Diamond (WTD) is a junction of several railway lines, all intersecting at the same grade (Figure 1). A major grade separation project at this site commenced in 2006 and is scheduled to be completed in 2015. The whole of the work is comprised of multiple contracts, completed and/or ongoing, by different constructors. Once completed, a depressed corridor over 1000 metres long with over 23,500 m2 (face area) of retained earth will bring the CN tracks beneath the CPR tracks and eliminate a major bottleneck at the most heavily used rail crossing in Canada."